The conventional means for preventing drownings in private pools include the provision of fences with self-closing gates, pool covers and one or more alarm systems which rely on disturbance of the water level or some other circumstance.
Gates are left open, or no longer operate automatically, pool nets are forgotten and surface-sensitive devices and others are often initiated by cats, dogs and other harmless agencies.
It has therefore become important to provide a device which is reliable and gives parents and bystanders timely warning of a possible drowning or other accident in a pool, or in a yachting or other boating or shipping activity.